It has previously been proposed to use water-hardenable materials such as resins in orthopaedic supports and casts; and typical patents disclosing such products include U.S. Pat. No. 4,996,979, granted Mar. 5, 1991, and U.S. Pat. No. 4,683,877, granted Aug. 4, 1987. However, when materials as disclosed in these patents are employed, the flow of liquid through the open cell foam or layers of fabric, as well as the strength of the orthopaedic support may not be subject to the desired level of control.
It is also noted that these prior art products mentioned above have other problems. Thus, for example with regard to the casts or supports using layers of material, care must be taken to firmly engage the layers during the exotherm portion of the setting period to ensure unitary bonding of the entire layered cast or assembly. Doctors practicing in this area even have a saying: "rub it like you love it," to encourage full engagement of the layers during hardening of the water-hardenable material. This step obviously requires care and expertise, as it is undesirable to apply undue force to an injured limb involving a broken limb, for example. Further, if this technique is not properly employed, the layers will not fully bond together, and the cast or support will be weak, and the layers could separate. Also with regard to the hardenable splints or supports using open cell foam, they may lack sufficient flexibility and conformability to properly fit the three-dimensional parts of the anatomy requiring splinting or support.
Flat rigid panels have also been proposed using double-knit fabrics and hardenable resins, as indicated by U.S. Pat. No. 5,166,480, granted Nov. 24, 1992, and entitled "Knitted Fabric Panel Structure and Process of Manufacturing." Reference is also made to U.S. Pat. No. 5,807,295, which discloses double-knit "Medical Articles." This patent includes a cursory disclosure of the use of medical material and water-hardenable material in double-knit material in certain specific simple configurations. Attention is also directed to U.S. Pat. No. 5,334,442, granted Aug. 2, 1994. This patent discloses an intermediate pliant sheet which may be made of a fabric such as glass fiber impregnated with a water-hardenable material. Then, on both sides of this pliant layer, the patentees disclose the use of layers of double-knit material. Thus, with double-knit material present in the assembly, it is not used to receive the water-hardenable material but is only used for padding.
As noted above, prior art orthopaedic products have involved shortcomings in the flow control of water to the water-hardenable material and the strength of the orthopaedic device.
Reference is also made to U.S. Pat. No. 4,770,299 granted Sep. 13, 1988, and entitled "Roll Form Medical Bandaging Product," which discloses a water-hardenable support. This '299 patent discloses a number of overlaid inner layers of fiberglass, which are impregnated with water-hardenable material, and an outer layer of a flexible, non-woven material, to form a protective layer adjacent the skin. This outer layer, which encloses the assembly, is water-permeable to permit wetting of the core which is impregnated with the water-hardenable material. However, this water permeability is somewhat undesirable, as it permits water or moisture to engage the skin, and the exothermic reaction accompanying wetting of the core may result in uncomfortable transmission of heat to the skin.
Concerning another aspect of the current practice of orthopaedic splinting and supporting, with layers of fiberglass being used for the water-hardenable core of the splints or supports, it requires considerable skill and practice to form splints or supports of varying thickness which may be required or which may be desirable for certain applications. Thus, for example, when a cast is to be provided for a foot and lower leg, it may be desirable to have greater thickness in the lower portion of the cast, and a lesser thickness in the vicinity of the shin or the calf of the user. With the present practice of using layers of fiberglass cloth, it requires considerable skill and practice to form a varying thickness layered cast or support which will have proper inter-layer bonding and strength.
Another problem encountered in this field is the fraying of the edges of material when cloth material, such as fiberglass, is cut. In this regard, following curing, the frayed edges may be hardened and may become sharp so that these sharp edges may injure adjacent soft tissue.